Beware lest there be a base thought in your heart, saying, "The seventh year, the year of release, is at hand," and your eye be evil against your needy brother and you give him nothing, and he cry out to Hashem against you, and it be sin in you.
English: "The year of release" — From the implication of the words "the seventh year" I would already know that it is the year of release; why then does the verse add "the year of release"? To teach you that there is another release that is similar to this one—namely, an ordinary loan whose term is not specified, which may not be claimed in less than thirty days.
On the daf / in context: Thirty days are treated as a full year for the purpose of this comparison, creating a secondary "release" period for unspecified loans.
Type of Learning
Derash on the verse (Sifrei) — an ordinary loan has a thirty-day minimum term.
What Is Learned
An ordinary loan whose duration was not stipulated may not be claimed before thirty days have elapsed.